Grent-'t-Jong Tineke, Oostenveld Robert, Medendorp W Pieter, Praamstra Peter
Department of Neurology, Radboud University Nijmegen Medical Centre, 6500 HB Nijmegen, The Netherlands, Donders Institute for Brain, Cognition, and Behaviour, Radboud University Nijmegen, 6500 HE Nijmegen, The Netherlands, and University of Glasgow, Institute of Neuroscience and Psychology, Glasgow G12 8QB, United Kingdom.
Donders Institute for Brain, Cognition, and Behaviour, Radboud University Nijmegen, 6500 HE Nijmegen, The Netherlands, and.
J Neurosci. 2015 Nov 11;35(45):15135-44. doi: 10.1523/JNEUROSCI.1329-15.2015.
Ethologically inspired models of movement preparation view the sensorimotor system as sampling information from the environment in a parallel fashion in preparation for multiple potential actions. In support, the configuration of the physical workspace, manipulated by the number or spatial separation of potential targets, has been shown to modulate sensorimotor neural activity. It is unclear, however, whether this modulation is driven by the sensory layout of the workspace or through the associated motor plans. Here, we combine a delayed-movement pre-cuing task with visuomotor adaptation to address this question in human subjects while recording MEG. By dissociating visual and motor coordinates of two targets using visuomotor adaptation, the task was designed to evaluate, in a selective fashion, the effects of visual and movement target separation on movement preparatory activity. The results did not allow the intended comparison due to an unanticipated effect of the direction of visuomotor adaptation on baseline oscillatory power in beta and low-gamma bands. Fortuitously, this effect was dependent on whether the adaptation direction decreased or increased the angular separation between alternative movements. That is, there was a sustained reduction of oscillatory power, which was stronger at small compared with large target separation. These results support a direct influence of movement target separation on motor cortex neural activity, mediated by lateral interactions between simultaneously active motor plans. The results further demonstrate a novel effect of visuomotor adaptation on motor cortex oscillatory activity, with properties that support the local nature of learned changes in visuomotor mapping.
There is growing evidence that the motor cortex routinely prepares for different movements simultaneously, each suited to a possible course of events in the immediate environment. The preparatory motor cortex activity for different movements can be seen as a competition between groups of neurons. This competition is influenced by how similar the alternative movements are; for example, in terms of direction, determined by the proximity of alternative movement goals. This study investigates whether the proximity of alternative reach goals has a direct influence on motor cortex activity (in the form of brain oscillations) or if it has an effect only through conscious evaluation of the separation between targets. We establish that there is a direct effect, supporting the biased competition model of action selection.
受行为学启发的运动准备模型将感觉运动系统视为以并行方式从环境中采样信息，为多种潜在动作做准备。支持这一观点的是，由潜在目标的数量或空间分离所操纵的物理工作空间配置已被证明可调节感觉运动神经活动。然而，尚不清楚这种调节是由工作空间的感觉布局驱动，还是通过相关的运动计划驱动。在此，我们将延迟运动预提示任务与视觉运动适应相结合，在记录脑磁图（MEG）的同时，在人类受试者中解决这个问题。通过使用视觉运动适应分离两个目标的视觉和运动坐标，该任务旨在以选择性方式评估视觉和运动目标分离对运动准备活动的影响。由于视觉运动适应方向对β和低γ频段基线振荡功率产生了意外影响，结果未能进行预期的比较。幸运的是，这种影响取决于适应方向是减小还是增加了替代运动之间的角度分离。也就是说，振荡功率持续降低，在小目标分离时比大目标分离时更强。这些结果支持运动目标分离对运动皮层神经活动的直接影响，这种影响由同时活跃的运动计划之间的侧向相互作用介导。结果进一步证明了视觉运动适应对运动皮层振荡活动的新影响，其特性支持视觉运动映射中学习变化的局部性质。
越来越多的证据表明，运动皮层通常会同时为不同的运动做准备，每个运动都适合于当前环境中可能出现的事件进程。不同运动的准备性运动皮层活动可被视为神经元群体之间的竞争。这种竞争受替代运动的相似程度影响；例如，在方向方面，由替代运动目标的接近程度决定。本研究调查替代伸手目标的接近程度是否对运动皮层活动（以脑振荡形式）有直接影响，或者它是否仅通过对目标之间分离的有意识评估产生影响。我们确定存在直接影响，支持动作选择中的偏向竞争模型。
